The invention relates to a trailer coupling for motor vehicles comprising a pivot bearing body which is rigidly attached to the vehicle and upon which there is mounted a pivotal element that is pivotal about a pivotal axis, a ball neck which extends outwardly from the pivotal element and carries a coupling ball at the end thereof remote from the pivotal element, and a locking device for fixing the pivotal element relative to the pivot bearing body in interlocking manner.
Trailer couplings of this type are known from EP 0 799 732 for example.
In the case of trailer couplings of this type however, a locking device of complex construction is required, said device additionally presenting problems in regard to the degree of free play.
Consequently, the object of the invention is to improve a trailer coupling of the type outlined above in such a manner that the locking device will be of the simplest possible construction and can be implemented in simple manner such that it is free of play.
In accordance with the invention, this object is achieved in the case of a trailer coupling of the type described hereinabove in that the pivotal element is mounted on the pivot bearing body in such a way that it is displaceable along the pivotal axis thereof, and in that, by virtue of a displacement of the pivotal element along the pivotal axis, the pivotal element is moveable into a position wherein it is pivotal relative to the pivot bearing body and into a position wherein it is fixed relative to the pivot bearing body in mutually non-rotatable manner by means of an interlocking arrangement.
The advantage of the solution in accordance with the invention is thus to be seen in the fact that it is now feasible for the pivotal element, which has in any case to be mounted such that it is moveable relative to the pivot bearing body, to be bestowed with an additional movement along the pivotal axis so that, by virtue of this additional movement, it is transferable from a position in which it is rotationally fixed relative to the pivot bearing body into a position in which it is rotatable relative to the pivot bearing body and vice versa.
Thus, the kinematic movements required for the pivotal movement and the fixing of the pivotal element are now transferred to this pivotal element in a constructionally particularly advantageous manner.
This is also especially advantageous for reason that there are no large forces effective on the pivotal element during the pivotal movement itself, so that the pivot bearing itself does not necessarily have to be constructed in such a manner as to accommodate all of the forces effective on the ball neck when in the towing mode, but rather, the interlocking fixing arrangement for the pivotal element can be formed in such a manner that it will accommodate an appreciable proportion of the forces effective on the ball neck when this is in its operative position.
In regard to the production of the interlocking arrangement, no detailed comments were made in the context of the previous explanation of the solution in accordance with the invention. Thus, it is particularly advantageous if the pivotal element is connected to at least one interlocking element in mutually non-rotatable manner so that this interlocking element will move with the pivotal element.
In such an arrangement, this first interlocking element could still be movable in a linear manner along the pivotal axis relative to the pivotal element for example.
Hence, it is particularly expedient if the at least one first interlocking element is arranged such that it is stationary relative to the pivotal element so that it would then be immovable relative to the pivotal element in both the direction of rotation about the pivotal axis as well as along the pivotal axis.
Furthermore, it is expedient if the pivot bearing body is connected to at least a second interlocking element which is substantially non-rotatable relative to the pivotal axis and, by means of which in conjunction with the first interlocking element, a rotational fixing of the pivotal element relative to the pivot bearing body is attainable.
The at least one second interlocking element could thereby be moveable relative to the pivot bearing body along the pivotal axis for example.
In order to obtain an interlocking arrangement for fixing the pivotal element relative to the pivot bearing body which is as free from play as possible, provision is preferably made for the at least one second interlocking element to be fixed immovably relative to the pivot bearing body.
In regard to the effect of the first and second interlocking elements in the case of an arrangement for fixing the pivotal element relative to the pivot bearing body, no detailed comments were made in connection with the previous explanation of the individual embodiments.
Thus for example, it would be conceivable to provide yet at least one further interlocking element for fixing the pivotal element relative to the pivot bearing body in mutually non-rotatable manner, said further interlocking element cooperating with the first interlocking element and also with the second interlocking element.
However, on grounds of providing a solution that is as constructively simple as possible, it is particularly expedient if the first interlocking element or the second interlocking element is adapted to be moved into engagement with the respective other interlocking element.
In order to obtain an arrangement for fixing the pivotal element relative to the pivot bearing body which is as free from play as possible when in the mutually non-rotatable position, provision is preferably made for at least one of the interlocking elements to comprise interlocking surfaces which taper in the direction of engagement, said surfaces serving to fix the pivotal element relative to the pivot bearing body in mutually non-rotatable manner.
The effect produced by these tapering surfaces is that it is thereby possible to create a play-free fixing arrangement which prevents rotational movement about the pivotal axis by a process of co-operation with a further interlocking element that adjoins these tapering surfaces.
In principle, these surfaces that taper in the direction of engagement could be constructed in any arbitrary manner. Thus, it would be conceivable to let these surfaces that taper in the direction of engagement extend parabolically or hyperbolically towards one another.
However, a constructively particularly simple solution envisages that the surfaces that taper in the direction of engagement should extend conically towards one another.
Such surfaces that taper in the direction of engagement have the disadvantage however, that they have a tendency to disengage again from the respective counter-acting surface upon the occurrence of large forces and especially of large torques when the wedge angle is greater than the wedge angle associated with a self-locking arrangement.
For this reason, a particularly expedient solution envisages that the interlocking elements should comprise interlocking surfaces which extend in parallel with the direction of engagement, this thereby preventing the interlocking elements from becoming disengaged in the face of excessively large forces or torques.
It is particularly expedient if these interlocking surfaces that extend in parallel with the direction of engagement adjoin the tapering interlocking surfaces so that, in the event that the interlocking elements are mutually displaced in a direction opposite to the direction of engagement due to the tapering interlocking surfaces, the surfaces extending in parallel with the direction of engagement will always ensure that the interlocking elements will remain in engagement.
In regard to the effectiveness of the interlocking elements, it is conceivable, for example, to construct them in such a manner that they are effective in one direction, whereas, for example, additional interlocking elements, for example in the form of stop members, lead to a blocking action in the other direction of rotation.
However, one particularly expedient solution provides for the pivotal element to be fixable relative to the pivot bearing body in two mutually opposite directions of rotation by means of the interlocking elements.
In accordance with the invention, one of the interlocking elements is constructed in the form of a projection which engages in the corresponding other one of the interlocking elements.
A projection of this type could be in the form of a tooth, a cam or a stud for example.
In connection with the previous explanation of the individual embodiments of the solution in accordance with the invention, no details have as yet been given in regard to the position in which the ball neck should be fixed in mutually non-rotatable manner relative to the pivot bearing body by the pivotal element.
Hereby, provision is preferably made for the pivotal element to be fixable in mutually non-rotatable manner relative to the pivot bearing body by means of the interlocking elements in at least the operative position of the ball neck.
In connection with the previous explanation of the solution in accordance with the invention, no detailed commentary has as yet been given as to how the process of fixing the pivotal element in the relevant position along the pivotal axis should be effected.
Thus for example, it would be conceivable to establish the individual positions as defined by an interlocking arrangement.
However, in order to make it possible to implement a play-free, mutually non-rotatable arrangement for fixing the pivotal element relative to the pivot bearing body in advantageous manner, provision is preferably made for the interlocking elements to be restrainable in the position thereof in which the pivotal element is fixed in mutually non-rotatable manner relative to the pivot bearing body by means of a wedge mechanism.
Restraint of the interlocking elements by an arrangement of this type serves to substantially eliminate the play whereby an arrangement for fixing the pivotal element relative to the pivot bearing body in play-free is thus obtained.
In regard to the construction of the pivot bearing body for the purposes of producing an interlocking arrangement for fixing the pivotal element, no extensive comments were made in connection with the previous explanation of the individual embodiments. Thus, it is particularly expedient if the interlocking elements are arranged between the pivotal element and a bearing element (also referred to herein as a xe2x80x9cbearing cheekxe2x80x9d) of the pivot bearing body, and if the wedge mechanism is effective on the pivotal element on the one hand and on the bearing cheek on the other, whereby the pivotal element will be restrained against the bearing cheek by means of the wedge mechanism.
It would be conceivable for example, for the wedge mechanism to be effective indirectly on the bearing cheek supporting the at least one second interlocking element, for example, via a further bearing cheek provided on the pivot bearing body.
However, one particularly expedient solution provides for the wedge mechanism to engage the bearing cheek directly and thus restrain the pivotal element against this bearing cheek.
This solution has the great advantage that the pivot bearing body does not have to serve for diverting away the forces required for restraint purposes, but rather the forces are effective substantially between the pivotal element and the bearing cheek due to the direct effect of the wedge mechanism on the bearing cheek supporting the at least one second interlocking element, the remaining section of the pivot bearing body being unaffected by those forces that are required for restraint purposes.
A wedge mechanism of this type can be constructed in the most varied of manners.
One manner of implementing a wedge mechanism of this type would be by the use of an eccentric.
One form of wedge mechanism that has proved to be particularly expedient is one wherein the wedge mechanism is formed by two interengaging threads since such an arrangement is adapted to be driven in a simple manner, and in particular, by means of an electric motor drive.
In principle, it would be conceivable within the framework of the solution in accordance with the invention to employ a wedge mechanism merely for the purposes of restraining the interlocking elements.
However, it is particularly expedient if a wedge mechanism is provided for the purposes of producing the movement of the pivotal element along the pivotal axis relative to the pivot bearing body.
Basically, a wedge mechanism of this type could differ from the wedge mechanism that serves to restrain the interlocking elements.
However, a particularly expedient solution envisages that the selfsame wedge mechanism should serve for the displacement of the pivotal element relative to the pivot bearing body on the one hand, and also for restraining the interlocking elements on the other.
In regard to the wedge mechanism provided for the displacement of the pivotal element, it is likewise expedient if this is formed by two interengaging threads.
In principle, it would be conceivable within the framework of the solution in accordance with the invention for the displacement of the pivotal element relative to the pivot bearing body to be effected manually.
Furthermore, it would also be conceivable for the process of fixing the pivotal element in the relevant position relative to the pivot bearing body to be performed manually, i.e. a manual process of fixing it in the mutually non-rotatable fixed position or in the rotational position.
However, it is particularly expedient if the pivotal element is movable along the pivotal axis between the individual positions by means of a motorised drive, preferably by means of an electric motor.
Furthermore, it is likewise advantageous within the framework of the solution in accordance with the invention if the achievement of freedom from play when fixing the pivotal element relative to the pivot bearing body in mutually non-rotatable manner is effected by means of a motorised drive so that the process of fixing the pivotal element in the relevant position is achievable in motorised manner.
A wedge mechanism, which is used either for moving the pivotal element relative to the pivot bearing body or for restraining the interlocking elements in the position wherein the pivotal element is fixed non-rotatably or which is used for both of these purposes, has proved to be advantageous, especially in the case where a motorised drive is provided.
Hereby, a wedge mechanism in the sense of this invention should be understood as being a mechanism which functions with a wedge surface that extends at an angle to the direction of movement thereof. Wedge mechanisms of this type are, for example, sliding wedge drives, cam drives, eccentric drives or helical drives.
As yet, no particular details have been given in regard to the manner of initiating the pivotal movement of the pivotal element into the position thereof wherein it is rotatable relative to the pivot bearing body.
For example, it would be conceivable to pivot the pivotal element into the position thereof wherein it is pivotal relative to the pivot bearing body by manual action.
However, it has proved to be particularly expedient if, in the position thereof wherein it is pivotal relative to the pivot bearing body, the pivotal element is pivotal by means of a motorised drive, preferably by means of an electric motor, between an operative position and a rest position.
A motorised drive of this type may be a pivoting drive which is provided exclusively for the pivotal movement of the pivotal element.
However, as an alternative thereto, it is also possible to derive the pivoting drive from a motorised drive which is effective for the displacement of the pivotal element along the pivotal axis between the individual positions.
It would be conceivable for example, for this to be done by switchable couplings so that a displacement of the pivotal element relative to the pivot bearing body along the pivotal axis is achievable by means of a motorised drive on the one hand, and, for example, a pivotal movement of the pivotal element into the position wherein it is rotatable relative to the pivot bearing body is effected by means of the switchable couplings.
For reason of providing a solution that is as constructively simple as possible, another advantageous embodiment of the solution in accordance with the invention envisages that the pivoting drive be coupled via a torque producing coupling to the motorised drive that is used for the movement of the pivotal element between the mutually non-rotatable fixed position and the position in which it is rotatable relative to the pivot bearing body.
A torque producing coupling of this type may, for example, be a coupling which unlatches when a maximum torque is exceeded, or, it may be a friction clutch which does not simultaneously block the motorised drive that is used for the displacement of the pivotal element between the various positions when the pivotal movement of the pivotal element is blocked by means of stop members for example, but rather which makes it possible for the system to continue to run despite the blocked pivotal movement of the drive and is thus in the position of being able to move the pivotal element from the position wherein it is rotatable relative to the pivot bearing body into the mutually non-rotatable fixed position and vice versa despite the blockage to the pivotal movement.
In regard to the mounting of the pivotal element relative to the pivot bearing body, no detailed comments were made in connection with the previous explanation of the individual embodiments.
Thus, one particularly advantageous embodiment provides for the pivotal element to be mounted on the pivot bearing body by means of a bearing pin.
It is particularly expedient thereby if the pivotal element is rotatable relative to the bearing pin so that it is possible to have a relative movement therebetween.
When using a bearing pin, it is particularly expedient if a displacement of the pivotal element between the individual positions is attained by means of a displacement of the bearing pin.
In particular, it is thereby additionally possible to restrain the interlocking elements in the operative position by applying tension or pressure to the bearing pin for example.
However, when using a bearing pin relative to which the pivotal element is rotatable, it is also possible in the case of a constructively particularly expedient solution to mount the bearing pin in the pivot bearing body in such a manner that it is rotatable and to achieve a pivotal movement of the pivotal element relative to the pivot bearing body via the bearing pin.
It is particularly expedient thereby if a torque producing coupling is provided between the rotatably driven bearing pin and the pivotal element so that, by virtue of a rotatable drive for the bearing pin, the possibility then exists of pivoting the pivotal element between two stop members, for example, a stop member in the operative position and a stop member in the rest position, without the motorised drive then becoming blocked upon arrival at the position of the stop members.
This is especially advantageous in each of the solutions wherein the displacement of the pivotal element as well as the pivotal movement of the pivotal element is attainable by means of a single motorised drive.
In connection with the explanation of the individual embodiments of the solution in accordance with the invention, no details have as yet been given in regard to the positions of the pivotal element relative to the pivot bearing body. Thus, one particularly advantageous solution envisages that the pivotal element be movable along the pivotal axis between a position in which it is pivotal relative to the pivot bearing body and a holding position in which the pivotal element is fixed to the pivot bearing body in mutually non-rotatable manner.
That is to say, that in the case of this solution, there are provided at least two positions of the pivotal element relative to the pivot bearing body between which the pivotal element is movable backwards and forwards by means of a displacement along the pivotal axis. A particularly preferred solution thereby provides for the pivotal element to be in said one holding position both in the rest position of the ball neck as well as in the operative position of the ball neck.
That is to say, that in the case of this solution, the pivotal element is movable along the pivotal axis out of the holding position so as to enable it to be pivoted about the pivotal axis, for example from the rest position into the operative position or from the operative position into the rest position, and thereafter, to effect a movement of the pivotal element into the holding position so as to fix it relative to the pivot bearing body in interlocking manner.
Another advantageous solution provides for the pivotal element to be in a first position in the rest position of the ball neck, and for the pivotal element to be movable from said first position into the pivotal position and from the pivotal position into the holding position in which the ball neck is in the operative position.
That is to say, that in the case of this solution, there are provided at least three differing positions of the pivotal element between which this pivotal element is movable back and forth along the pivotal axis by a displacement process, whereby the first position and the holding position are arranged at opposite sides of the pivotal position so that a transfer from the rest position into the operative position or from the operative position into the rest position is effected by means of a movement in just a single direction, whereby, on each occasion, the pivotal position between these positions is reached wherein the pivotal movement of the ball neck from the operative position into the rest position can be effected.
In regard to the first position, no detailed comments have been made as to the manner in which the pivotal element could be fixed. For example, it would be conceivable to drive the pivotal element by means of a self-locking drive arrangement and to fix it in the first position simply by means of the self-locking action of the drive.
However, as the trailer coupling is intended to remain in the rest position for long periods of time and should be retained properly in this position, it is advantageous if said first position is likewise a holding position in which the pivotal element is fixed relative to the pivot bearing body in mutually non-rotatable manner.
This fixing process could be effected in a non-positive manner for example. However, it is particularly expedient if the pivotal element is fixed relative to the pivot bearing body in said first position by an interlocking arrangement, whereby the interlocking action does not have to be produced directly between the pivot bearing body and the pivotal element. It is also conceivable to provide the interlocking arrangement in the vicinity of the ball neck or in the vicinity of other elements, for example, of a stop cam.
In connection with the solution in accordance with the invention, we have not as yet gone into the operation thereof when using one or more motorized drives.
Thus, one particularly advantageous solution for the trailer coupling in accordance with the invention envisages that it should comprise a control system, and that the movements of the pivotal element from the operative position into the rest position and vice versa should be adapted to be monitored by said control system by means of at least one sensor.
In particular, provision is hereby made for the control system to interrupt the pivotal movement in the event of the control system detecting a deviation of the movement of the pivotal element from the predefined form of movement.
In accordance with the invention, such a deviation of the movement of the pivotal element from the predefined form of movement can be advantageously implemented, in particular, if the individual positions of the pivotal element are detectable by means of the sensor.
For example, it would be conceivable to constantly monitor the movements of the pivotal element by means of the sensor so as to ascertain whether they deviate from the predefined form of movement.
This can be implemented in a particularly expedient manner if the predefined movement of the pivotal element is capable of being monitored by a process of scanning a slider track that is correlated therewith.
In this case for example, the slider track can be shaped such that the sensor will not emit a signal when it can follow the slider track without hindrance whereas the sensor will emit a signal when there is a deviation from the slider track.
In order to enable the drive to be switched off in good time, especially in the case of a single drive, provision is preferably made for the control system to comprise a current monitoring arrangement for the motorised drive, and for the control system to interrupt the drive in the event that a predetermined maximum current level is exceeded.
The drive can thereby be switched off in a simple manner, for example, in the end positions.
Furthermore however, another conceivable possibility in the case of this solution is that of switching off the drive if the ball neck encounters an obstruction, the user of the motor vehicle for example, during the course of its pivotal movement.
Furthermore, the solution in accordance with the invention comprising the process of switching off the drive has the advantage that differing threshold values can be associated with the different phases of the movement, so that, for example, a high starting torque will be made available when starting the drive by virtue of a high threshold value, whereas, in each of the phases in which one might reckon with a collision between the ball neck and a part of the body of the user, the threshold value is set at a lower level.
Further features and advantages of the invention form the subject matter of the following description and the sketched illustration of several embodiments.